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This paper describes the development of the electronically controlled governor system for the Toyota X300 forklift truck whose load capacity is 1 to 3 tons with two gasoline engine models. With this governor system, the maximum engine power was significantly improved. In addition, the maximum vehicle speed as well as the maximum lifting speed can be adjusted. In this governor system the accelerator is electronically connected to the throttle valve of the carburetor. The electronic control unit then actuates the throttle valve in order to maintain the engine at a target speed. This paper also describes the development of software in association with the governor system. As the control method, the Proportional-Integral-Derivative (PID) method was chosen because of its easiness in use. An auto-tuning system was developed to attain the best combination of the controlling parameters of the PID method, satisfying the required response and stability in the engine speed.

An electronically controlled governor was developed for a generator equipped with a medium size gasoline engine. Among the available control methods, LQ and PID were considered since they are high practical and require less computations. Based on a numerical simulation, the PID control method was chosen for the governor system because of its simplicity in tuning the control parameters. To ensure the reliability of the governor system for volume production, the system has been tested with regard to the influence of environmental changes, and the deviation of engine performance and its deterioration. Under all of the above severity tests, the governor system has been confirmed to provide an excellent performance and stability in the power output far exceeding the ISO-A1 standards.